HAL Id: in2p3-00185304
http://hal.in2p3.fr/in2p3-00185304
Submitted on 5 Nov 2007
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of
sci-entific research documents, whether they are
pub-lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
GANIL RF system
C. Bieth, G. Duguay, A. Joubert, C. Pagani, J.M. Baze
To cite this version:
C. Bieth, G. Duguay, A. Joubert, C. Pagani, J.M. Baze. GANIL RF system. 8th Particle Accelerator
Conference, Oct 1979, San Francisco, United States. pp.4117-4119. �in2p3-00185304�
IEEE Transactions on Nuclear Science, Vol. NS-26, No. 3, June 1979 GANIL* RF SYSTEMS
C. BIETH, G. DUGAY, A. JOUBERT, C. PAGAN?, J.M. BAZE
Abstract 1.2 Mechanical studies
Final studies on a model were made simultaneous- The external OFHC copper wall, divided into three ly for the tpree types of GANIL resonators : separated sector removable parts, is supported by a stainless steel structure cyclotrons , injector cyclotron2 and buncher no 13, These which allows the copper to expand and keeps the geometrical investigations have permitted complete definition of the main relation between dee and anti-dee constant. These structures parameters of these resonators (size, tolerances, current are connected together to a support, which is placed on three and voltage distribution, losses, coupling and tuning). Me-
chanical studies for the three resonators are nearly finished. Technological studies on sliding contacts have been made at full current. Phase and amplitude regulation systems have also been tested. The values measured fully satisfy GANIL tolerances. Construction of the first two resonators of CSS, CO and buncher will start in July 1979. At the same time the prototype of a 100 kW RF transmitter has been satisfactorily tested and construction of the first three amplifiers will begin soon.
1, Separated sector cyclotron resonators 1.1 Model measurements
Q-value, frequency variation with capacitive panel, voltage distribution along the gap, coupling loop and tuning methods have been investigated on the 1 : 3 scale model (Fig, 1). These results are in good agreement with those calculated. The 1 : 3 model has also been used to define current distribution in the inner and outer conductors, espe- cially in the region of the movable capacity stem where a uni- form density of the current in the sliding contacts is very im- portant. From these measurements total power losses have been re-evaluated and the size of the movable capacity stem has been adjusted to reduce the maximum current density at 20 A/cm. For 250 kV at 14 MHz, the maximum power will be less than 80 kW and for 100 kV at 6 MHz, less than 60 kW.
jacks mechanically insulated from the vacuum tank.
2 Fig.
The three-dimensional calculations using the finite elements method4, including the thermal field action and the stainless .el structure, have shown that the maximum dis-
Fig. 1
placement of the anti-dee lips is in the order of 0.6 mm i vertical direction (Fig. 3).
n the
3 Fig.
x
Grand Accelbrateur National d’Ions Lourds. Project sup- ported jointly by Commissariat & I’Energie Atomique (CEA) and Institut National de Physique Nucleaire et de Physique
des Particules (I N2 P3). The movable capacitive panel is moved by a hydrau- GANIL - B.P. 5027 - 14021 CAEN CEDEX - FRANCE lit jack with an internal drive. Movement resolution is lees than l/100 mm. H
From 1st. Nazionale di Fisica Nucleare, Milan0 - Italic
4117 0018-9499/79/0600-4117$00.75 0 1979 IEEE
© 1979 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers
1. 3 Power amplifier and coupling
As the inductive coupling loop is fixed, its impe- dance varies with the frequency : 25R at 6 MHz and lOOn at 14 MHz. To match this impedance with the load impedance of the tube, we use a tunable plate tank circuit (‘II ) with two variable capacitors. The RF power on the grid of the final stage (1.5 kW) is given by another single tetrode tube with a “fl in the plate circuit, The impedance ratio is 2000/50 with 650 pF on the grid circuit. This circuit uses only one varia- ble element (impedance). The grid of the pre-amplifier is driven by a wide-band amplifier (100 W). The actual proto- type amplifier5 has delivered more than 120 kW in the range
6 to 14 MHz (Fig. 4).
fwPlIfIIArfuR
Hi 100
k&
cz- J0.m~ ,I Il.. I,LqH t'r,C5..20 IUUUp~ I &2DyH C3-45;pl C4-140pl 1; us f,ZqH C’G..hOpl 1 fd a qn C6-65cpr RI:RZ. W - cl- II 650~: ” Cl. MO/’ 1.4-rdor *6’b
Fig. 4 Phase and amplitude regulationFig. 5 shows the GANIL RF control system (for one SSC). We expect the following values for the accuracy of the dee voltage :
- fast self-tuning system : phase accuracy i 1” RF phase with a bandwidth for small detunings greater than 20 Hz and a slew-rate of 120” RF per second
- amplitude stabilization : less than 2 5. 10m5 for bV/V, long-term drift and ripple. A special dynamic filter will certainly be necessary to reduce parasitic AM introduced by the 50 Hz harmonics, especially the lst, 2nd and 6th harmonics
- phase stabilization : less than $ 0.15”. A special beam phase input signal has been made to reduce the energy spread after each SSC if necessary,
5 Fig.
La-
PItASIRfmUC I mtruof RrmENrE
I
Fy~*y~;;;j
GM1 Rf FEEDBACK
lONJROL
LOOP& M~V/N~
1.5 Experimental studies 1.5.1 Experimental resonator -- -_-_----_--- - ----
All the experiments described here were made with our 3 meter quarter-wave resonator powered by a 25 kW RF amplifier. On the variable capacity, current and voltage as high as 170 kV peak and 1100 A peak can be reached to test sliding contacts or sparking problems. Tuning, phase and amplitude regulation systems were also tested, - 1.5.2 Amplitude and phase regulation ---
For the amplitude regulation, numerous tests were made with a classical compensation network. This feed-back control systems has a unity gain bandwidth at 4060 Hz. A special phase shifter has been designed for the phase regula- tion? Its essential characteristics are : very low harmonic distortion, low’phase noise (4 0. Pl“), bandwidth (small sig- nals) greater than 25 kHz, phase shift capability + 40”, RF output voltage constant and independent of the phase shift, frequency range 6 to 20 MHz.
Included in the phase loop control system of the test tank (unity gain bandwidth near 60 kHz upto 100 Hz) a resi- dual parasitic phase modulation less than t 0.03” has been obtained (at 16 MHz for this test). Fig. 6 shows the spec- trum analysis of the RF voltage at 16 MHz (scan width 100 Hz/div. ), which is characteristic of the residual phase modulation and noise (the AM main spikes are 12 dB down).
n ” f 10 5 p 20 $0 zi 40 50 - 1000 Ii3 - 500 Co +500 t too0 5PECWM ANAlYS/S at -16 8.~1’3 6 Fig. 1.5.3 Sliding contacts --- ---
For the GANIL resonators the mechanical tolemn- ces are such that we need a contact with a transversal elon- gation in the range of i 1 mm and with a current density around 20 A/cm. Small movements with the RF on are also necessa- ry to correct thermal expansion of the resonators. Various types of commercial sliding contacts have been tested, but they are not able to meet all our requirements. In collabora- tion with CGR-MeV we are therefore developing a special type of contact using silver graphite contacts (95 8 silver) and bronze beryllium or cobalt beryllium bronze blades. The first results are good, both for current density and lifetime, (Fig. 7).
Temp/
N finger Intensity fingrr Remarks /cm Ajfinge r ‘C 2 11.5 4 60 no dammage after 1 23 4 80 7 60 hours I 4118
Fig. 7
2, Injector cyclotron resonators
The same studies have been made on the 1 : 4 model as for the SSC resonators, Compared with the calcu- lations, minor modifications have been included in the stem length and size, Most of our measurements have been devo- ted to the density current in the sliding contacts and to the choice of the shape of the movable stems. The profile given on Fig. 8, which also shows the maximum current density lower than 23 A/cm, is a good compromise.
0 - IO - 20 - 30 , A/CM CONTACT c”mm‘NT CmNmtTY >- e.---- . . \ /- \ 8 Fig. 9 Fig. \ \ \ \ \ \ \ \ \ \ \ \ \ I I I Iman 22Alcm - 10 Fig.
Mechanical studies will be finished in two months and Fig. 9 shows a full-scale model of the “waved” panel’.
3. Buncher no 1
This buncher is placed between the injector cyclo- tron and the first SSC. A 1 : 2 model has been built and the results are in good agreement with the calculations, Fig. 10.
The main characteristics are :
- maximum voltage on the electrode : 130 kV to 14 MHz - frequency range 6 to 14 MHz by symmetrical movement
of flat capacitive panels - maximum power losses : 20 kW - amplitude stability ? 1 % - phase stability 5 0.5”.
References
1. C. Bieth, Le systBme acchlerateur du GANIL l&re partie, GANIL 78R/053/HF/02
2. C. Bieth, A, Joubert, C. Pagani
Le systeme acc&?rateur du cyclotron injecteur du GANIL GANIL 79R/024/HF/06 (to be published)
3. C. Pagani, Le regroupeur no 1, GANIL 78N/115/HF/OB 4. J.M. Baze, Calculs du comportement du resonateur
haute frbquence, GANIL 79R/019/ME/02 5. G. Dugay, Amplificateur HF 100 kW 6 & 14 MHz,
GANIL 79N/017/HF/05
6. A. Joubert, B. Ducoudret, Etude du systeme d’accord rapide asservi pour l’injecteur CO, GANIL 78N/004/HF/Ol 7. A. Joubert, Essais de contact VARIAN CF 500,
GANIL 78N/149/HF/15.
8. A. Joubert, Stabilisation en phase d’un resonateur CSS, GANIL 79R/034/HF/09
